This application claims the priority benefit of Taiwan application serial no. 89,102,694, filed Feb. 17, 2000.
1. Field of the Invention
The present invention relates to a method of controlling an optical disk system. More particularly, the present invention relates to a method for detecting the running speed of a sledge motor inside an optical disk system.
2. Description of Related Art
The optical pickup head of most optical disk system such as a compact disk-read only memory (CD-ROM) drive or digital versatile disk (DVD) drive must track before reading data from the optical disk. At present, CD-ROM is only capable of detecting the velocity feedback signal in long track jumps. In newer CD-ROM and DVD system, a feedback signal of error tracking can be detected using a photo-interrupt method instead of velocity feedback.
FIG. 1 is a conventional control circuit diagram of a sledge motor and an actuator. As shown in FIG. 1, the sledge motor 18 is coupled to the actuator 20. The actuator 20 is capable of driving an optical pickup head 22. The sledge motor 18 and the actuator 20 are driven by a power driver 16. The running speed of the sledge motor 18, the running speed of the actuator 20 and the run-out speed of the disk are amplified by a pre-amplifier 10. Signal from the pre-amplifier 10 is fed back to a track/velocity sensor 12. The track/velocity sensor 12 generates velocity feedback signal to a seek control circuit 14 according to the signal from the pre-amplifier 10. As soon as the seek control circuit 14 picks up information including the velocity feedback signal, the jump track command and the track number, a track servo output (TRO) signal and a sledge motor voltage output (FMO) signal are produced. The TRO signal and the FMO signal are fed to a power amplifier 16 so that motion of the actuator 20 and the sledge motor 18 are in control.
FIG. 2 is a schematic diagram showing a long track jumping and a short track jumping of an optical pickup head. In a long track jumping, after the seek control circuit 14 picks up data including the velocity feedback signal, the jump track command, the track number, the pick-up head moves from position A to position B. In other words, the optical pickup head moves from track 30a to track 30b of the disk 30. Similarly, in a short track jumping, tthe pick-up head moves from track 30b to 30c. 
In general, the velocity feedback signal of long track jumping in an optical storage device is equal to the vector sum from the running speed of the sledge motor, the running speed of the actuator and the run-out speed of the disk. Before any track-jumping operations are carried out, speed of the driving motor must first be known. Track jumping is best when the motor is motionless or moves slowly both in beginning and end of the track jumping. However, the velocity feedback signal for a long track jumping of the optical pickup head includes the running speed of the actuator and the run-out speed of the disk as well. Hence, it is probably to detect a relatively high speed when the motor is stopped. In other words, the actual speed of the motor is difficult to detect. Without the precise running speed of the motor, subsequent tracking after a track-jumping operation is not made and reading from the optical disk system is delayed.
In brief, since a conventional optical disk system cannot detect the actual running speed of the sledge motor or decide if the motor is stationary after a track-jumping operation, subsequent tracking of the optical disk system is difficult.
Accordingly, one object of the present invention is to provide a method for detecting the running speed of a sledge motor within an optical disk system by removing velocity feedback signal produced by other elements.
A second object of this invention is to provide a method for controlling an optical disk system. By eliminating other velocity feedback signals contributed by other sources, running speed of the motor can be obtained.
A third object of this invention is to provide a method for detecting the running speed of a sledge motor within an optical disk system by simulating the tracking servo output signal. Consequently, only the velocity feedback signal produced by the sledge motor is retained and hence accurate track jumping is obtained.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method for detecting the sledge motor running speed in an optical disk system. A method for detecting the speed of a sledge motor in an optical storage device. In response to a track jumping command, a tracking servo output signal is expanded onto an orthogonal space to obtain simulation parameters corresponding to the tracking servo output signal. A pseudo-tracking servo output signal is generated according to the simulation parameters of the tracking servo output signal. Then, the pseudo-tracking servo output signal is used to compute the speed of the sledge motor.
The orthogonal space can be established through sine and cosine functions so that amplitude and phase of the tracking servo output signal becomes amplitude and phase of the pseudo-tracking servo output signal. Furthermore, the pseudo-tracking servo output signal is obtained from various sampling intervals so that the pseudo-tracking servo output signal and the tracking servo output signal have a similar waveform.
In this invention, the velocity components within the velocity feedback signals not generated by the sledge motor are eliminated by the pseudo-tracking servo output. Hence, running speed of the sledge motor can be determined accurately, and track-jumping operations can be carried out efficiently within the compact disk system.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.